Ignition system



Nov. 26, 1968 3. 0. HUNTZINGER 3,412,723

IGNITION SYSTEM Original Filed Oct. 17, 1963 3 Sheets-Sheet 1 INVENTQRS' Gerald 0. Hun/zinger BY Ralph E. Tar/er Kafka/(WM ATTORNEY N v- 2 9 G. o. HUNTZINGER ET AL 3,412,723

IGNITION SYSTEM Original Filed Oct. 17, 1963 3 Sheets-Sheet INVENTORS Gerald 0. Hun/zinger BY Ralph E. Tar/er mum A Home y 1968 s. o. HUNTZINGER ET 3,412,723

IGNITION SYSTEM Original Filed Oct. 17, 1963 5 Sheets-Sheet C5 INVENTQRS Gerald 0. Hunfz/nger Fig. 6 BY Ralph E. Tarfer zwum Attorney United States Patent 3,412,723 IGNITZON SYSTEM Gerald O. Huntzinger, Anderson, Ind., and Ralph E. Tarter, Richardson, Tex., assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Original application Oct. 17, 1963, Ser. No. 316,815, now Patent No. 3,320,939, dated May 23, 1967. Divided and this appiication May 2, 1967, Ser. No. 635,438 7 Claims. (Cl. 123-448) ABSTRAtIT 0F THE DISCLOSURE In a preferred form, an ignition system including a semiconductor controlled rectifier switch for discharging current through an ignition coil is provided with a circuit connected to the controlled rectifier control electrode which includes a transformer having a primary winding connected in series with a pair of breaker contacts and a secondary winding connected in circuit with a capacitor and the control electrode. When the breaker contacts open the controlled rectifier is switched off and then back on before the contacts reclose.

This is a division of application Ser. No. 316,815, filed Oct. 17, 1963, now Patent No. 3,320,939, issued May 23, 1967.

This invention relates to ignition systems for internal combustion engines and more particularly to an ignition system that has a semiconductor control means for controlling primary winding current and wherein the control means is of a type that can be switched between the conductive and nonconductive conditions by switching pulses of opposite polarity.

In the conventional ignition system for motor vehicle engines, it has been common practice to use an ignition coil which has a primary winding and a secondary winding. The secondary winding is connected with the spark plugs of the engine through a distributing means which has taken the form of a rotatable rotor that cooperates with the inserts or electrodes of a distributor cap. The primary winding is energized from the source of direct current on the motor vehicle and primary circuit is periodically interrupted by breaker contacts which open and close in synchronism with the engine. The breaker contacts are controlled by a breaker cam which causes the contacts to open and close in a predetermined sequence.

Although the above described conventional ignition r system has for the most part performed in a satisfactory manner, it has certain disadvantages. One of the disadvantages of this system is that the primary current for the primary winding of the ignition coil must flow through the breaker contacts with the result that the breaker contacts become burned and pitted by arcing. In addition, the breaker contacts are constantly engaging and disengaging each other which provides some mechanical wear. As a result, it is necessary to periodically replace the breaker contacts in order to achieve optimum performance from the engine.

Even where the breaker contacts are kept in good condition by periodic replacement, the conventional ignition system has certain limitations in that the primary current must be maintained below some predetermined value in order to achieve relatively long life for the breaker contacts. If the breaker contacts are overloaded to provide higher output voltage for the secondary winding of the ignition coil, their life span is reduced with the result that as a practical matter, the amount of current that breaker contacts can handle and therefore the 3,412,723 Patented Nov. 26, 1968 ice amount of output voltage that can be delivered by the secondary winding of the ignition coil is limited.

Another disadvantage of the conventional contact breaker system is that the time the contacts are closed per cycle of operation grows shorter as engine speed increases which may afiect engine performance. An eight cylinder engine usually has eight lobe breaker cam op erating at half engine speed. Such a cam repeats its cycle of events each degrees of rotation and in each cycle the contacts may be closed for 32 degrees of rotation and open for 13 degrees, the latter being about minimum for satisfactory operation.

In contrast to the above described conventional ignition system, it is an object of this invention to provide an ignition system wherein the current flow through the breaker contacts is greatly reduced and wherein it is possible to close the primary circuit for the ignition coil before the breaker contacts close to provide the maximum amount of time that the primary circuit is closed during a given cycle of operation. In carrying this object forward, a semiconductor element is provided which is connected in series with the primary winding of the ignition coil. This semiconductor element preferably takes the form of a silicon controlled rectifier which is capable of being switched on and off by voltage pulses being applied to its gate or control electrode.

A further object of this invention is to provide an internal combustion engine ignition system wherein a switchable controlled rectifier controls primary current and wherein the system is provided with means for normally maintaining the controlled rectifier in a conductive condition and wherein means are provided for temporarily switching the controlled rectifier to a nonconductive condition when an ignition pulse is desired. In carrying this object forward, the controlled rectifier may be controlled by the conventional breaker points in an ignition system and the system is arranged such that a spark impulse may occur when the breaker points open, but the controlled rectifier can then be turned back on before the breaker points close.

Another object of this invention is to provide an ignition system wherein a switchable controlled rectifier controls primary winding current and wherein this controlled rectifier is normally biased to a conductive condition but is temporarily switched to a nonconductive condition by a control circuit which includes a two winding inductor such as a transformer which in turn is controlled by the conventional contacts of a distributor. In this system, a bias voltage is provided by the potential on a capacitor connected between the inductor and the gate or control electrode of the controlled rectifier. A voltage pulse is produced in one of the windings of the transformer causing charging and discharging of the capacitor such that the controlled rectifier is switched off and then on. This voltage pulse is timed in accordance with the opening of the breaker contacts of a conventional distributor.

Another object of this invention is to provide a transistor ignition system which is similar to that shown in the Hetzler patent, 3,034,019, but which differs from the disclosure of this patent in that the primary winding of the ignition coil is connected between the output electrode of the transistor and ground rather than between the input electrode of the transistor and one side of the source of the direct current. In the Hetzler patent and in the transistor system of this invention, a transformer is used to control the biasing of the transistor and with the circuit of this invention, a smaller transformer can be used since it takes less biasing voltage with the system of this invention to switch the transistor off.

Further objects and advantages of the present invention will be apparent from the following description,

reference being bad to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic circuit diagram of a switchable controlled rectifier ignition system rnade in accordance with this invention.

FIGURE 2 is a schematic circuit diagram of a modified controlled rectifier ignition system made in accordance with this invention.

FIGURE 3 illustrates a modification of FIGURE 2.

FIGURE 4 is a schematic circuit diagram of a modified version of FIGURE 3.

FIGURE 5 is a schematic circuit diagram of an ignition system that uses a transistor rather than a controlled rectifier for controlling primary winding current.

FIGURE 6 is a modified version of the system illustrated in FIGURE 5.

Referring now to FIGURE 1, the reference numeral 28 designates an internal combustion engine. This engine may be, for example, a six cylinder engine and one of the six spark plugs for the engine is designated by reference numeral 46. It will, of course, be appreciated that there will be five other spark plugs which are not illustrated and it also will be appreciated that the ignition system of this invention can be used with engines having other than six cylinders.

One side of the spark plug 46 is grounded whereas the opposite side of this spark plug is connected with conductor 44. The conductor 44 is connected with one of six electrodes 32 which may be, for example, the inserts or electrodes that are found in a conventional distributor cap. The electrodes 32 cooperate with a rotor contact 30 which is driven in synchronism with the engine 28 and which is electrically connected with a high voltage conductor 42. The conductor, as is well known to those skilled in the art, supplies spark impulses to the spark plugs 46 as the rotor contact 30 swings past the fixed contacts or electrodes 32.

The ignition system of FIGURE 1 has a pair of conventional breaker contacts 22 and 24-. The contact 22 is carried by a pivotally mounted breaker lever having a rubbing block which is engaged by a distributor cam 26. The contacts 22 and 24 are normally spring biased to an engaged position as is well known to those skilled in the art and the cam 26 periodically opens these contacts. The contact 24 is the fixed contact and is grounded as shown.

In practice, the breaker contact apparatus which include the contacts 22 and 24, the distributor cap contacts 32 and rotor may all be a single unit conventional distributor wherein both the rotor contact 30 and the cam 26 are driven by the engine 28. In this connection, it will be appreciated that the distributor may have the usual vacuum and centrifugal advance mechanisms if so desired.

The reference numeral 10 designates a source of direct current on a motor vehicle'which is shown as a battery. This battery will supply ignition power during cranking and when the engine is running at slow speeds and the ignition power during higher speed operation of the engine will be supplied by the usual generator which is not shown. One side of the direct current source 10 is grounded whereas the opposite side of this source of voltage is connected with a manually operable ignition switch 14 through conductor 12. When the ignition switch 14 isclosed, the conductor 16 is connected with the positive side of the direct current source 10.

The ignition system of this invention has a conventional ignition transformer or ignition coil designated by reference numeral 36. This ignition transformer has a primary winding 38 and a secondary winding 40. It is seen that one end of the secondary winding is connected with the conductor 42 which supplies spark impulses to the spark plugs 46 through the rotor contact 30 and the distributor cap electrodes 32. The opposite side of the secondary winding 40 is connected with junction 41. The junction 41 is connected with one side of the primary winding 38 by conductor 48 and also to one side of a capacitor 50*. The opposite side of the capacitor 50 is I grounded.

The switching element which is used in the system of this invention is a controlled rectifier generally designated by reference numeral 54. The controlled rectifier 54 has an anode 56, a cathode 60 and a gate or control electrode 58. This controlled rectifier is a PNPN semiconductor device and has the characteristic of being switched on and off by pulses of voltage applied between the gate and cathode of the controlled rectifier.

To be more specific, the characteristics of the controlled rectifier 54 are such that when the anode 56 is positive with respect to the cathode 6t and when a pulse of voltage is applied between the gate and cathode electrodes which drives the gate positive with respect to the cathode, the controlled rectifier turns on in its anodecathode circuit. This device is of a type that once the gate electrode is driven positive with respect to the cathode, it will remain turned on in its anode-cathode circuit even though the signal voltage is removed from the gate and cathode electrodes. Thus, a positive pulse of voltage which is a plied to the gate electrode will switch the controlled rectifier on and it will remain on even after this pulse of voltage is removed providing the anode is maintained positive with respect to the cathode.

On the other hand, the controlled rectifier 54 is of a type which will be switched off in its anode-cathode circuit when the gate electrode 58 is driven negative with respect to the cathode 6t and even though the anode is positive with respect to its cathode. In addition, the controlled rectifier 54 will remain in its switched off condition even after the negative pulse has been removed from the gate electrode and even though the anode is positive with respect to the cathode.

It can be seen from the foregoing that the controlled rectifier 54 has the characteristic of being switched on or off by positive or negative pulses applied between the gate and cathode electrodes and that the controlled rectifier will remain in the state to which it was switched even though the gate signal be completely removed. This is assuming that the cathode has not been driven positive with respect to the anode for under such a condition, the controlled rectifier will be turned 01f. It will be appreciated that this controlled rectifier is diiferent from certain controlled rectifiers which cannot be tuned ed by a negative gate signal. In this other type of controlled rectifier, it is necessary to drive the cathode positive with respect to the anode in order to switch the controlled rectifier off.

The controlled rectifier 54 has little or no voltage drop between its anode and cathode when in a conducting condition and preferably has a forward and reverse breakdolwn voltage rating in the neighborhood of 500 to 700 V0 ts.

The anode 56 of controlled rectifier 54 is connected with junction 41 and therefore is connected with one side of the primary 38 of ignition transformer 36. The cathode 60 of controlled rectifier 54 is grounded. The gate electrode 58 of controlled rectifier 54 is connected with a conductor 62.

The conductor 62 is connected with the secondary winding 68 of a two winding inductor or pulse transformer generally designated by reference numeral 64. This inductor or transformer 64 has a primary winding 66 and this winding and the secondary winding 68 are wound on a suitable magnetic core.

9 The primary Winding 66 of the pulse transformer 64 has one of its sides connected with a resistor 67. The opposite side of primary winding 66 is connected with a conductor 63 which is connected with the movable breaker contact 22. A capacitor 23 is connected between conductor 63 and ground. The resistor 67 is connected with junction 18 which in turn is connected with the conductor 16.

As noted above, one side of the secondary winding 68 of transformer 64 is connected with conductor 62. The opposite side of secondary Winding 68 is connected with junction 69 via conductor 53. A resistor 81 is connected between junctions 69 and 71. Another resistor 77 connects the junction 69 and ground. A current limiting resistor 70 is connected between junction 71 and the primary winding 33 of the ignition transformer 36.

When ignition switch 14 is closed, the ignition system of this invention is energized. With ignition switch 14 closed, a potential is applied across resistors 81 and 77 between junction 71 and ground. As a result of this, the poential of junction 69 will be positive with respect to ground and current will flow from junction 71, through resistor 81, through junction 69, through conductor 53, through secondary winding 63, through conductor 62, and through the gate to cathode junction of controlled rectifier 54. Since the gate electrode 58 of the controlled rectifier is now at a positive potential with respect to the cathode 66, the controlled rectifier is switched on in its anodecathode circuit. With the controlled rectifier switched on, current flows from the junction 71, through resistor 76, through primary Winding 38 of the ignition transformer and then through the anode-cathode circuit of controlled rectifier 54 to ground. it should be pointed out that the controlled rectifier 54 could be turned on even though the contacts 22 and 24 were disen aged since the biasing circuit comprised of resistors 81 and 77 provides a bias from the direct current source it) that normally maintains the controlled rectifier 54 in a turned on condition.

Assuming now that the engine is either being cranked so that the breaker cam 26 rotates or that the engine is running and driving the breaker cam 26, the breaker contacts 22 and 24 will be opened and closed in synchronism with operation of the engine 28. When breaker contacts 22 and 24 close, it is seen that current can flow from junction 18, through resistor 67, through primary winding 66 of transformer 64 and through the closed breaker contacts 22 and 24 to ground. When breaker contacts 22 and 24 close, and current flows through the pri mary winding 66, a voltage is induced in the secondary winding 68 which is positive at conductor 62 and negative at conductor 53. This voltage is of such a polarity as to provide an additional signal voltage for turning on the controlled rectifier 54 since this voltage aids in driving the gate 58 positive with respect to cathode 60. This additional voltage is helpful when the engine is being cranked since the voltage of source it) at this time drops.

When the breaker contacts 22 and 24 open, the circuit for the primary winding 66 of the transformer 64 is broken and as a result, a voltage of a reverse polarity is induced in secondary winding 68. This voltage is positive at conductor 53 and negative at conductor 62 and is sufficient to drive the gate electrode 58 negative with respect to the cathode 60. Because of this, the controlled rectifier 54 is switched off in its anode-cathode circuit which opens the circuit for primary winding 38. When the primary circuit for primary winding 38 is substantially opened, a voltage is induced in the secondary winding 40 which is applied to one of the spark plugs via the conductor 42, rotor contact 30, fixed distributor contacts 32 and conductor 44.

When the inductive energy of the transformer 64 is dissipated, the controlled rectifier 54 will turn back on even though the contacts 22 and 24 might still be open. Thus as soon as the turn off signal appearing across secondary winding 68 is dissipated, the controlled rectifier is immediately biased back to a conductive state by the positive voltage appearing at junction 69. This means that a longer on time for primary winding current can be achieved since controlled rectifier 54 can be switched back on immediately after the ignition pulse has occurred and before a reclosing of contacts 22 and 24. It will, of

course, be appreciated that when the contacts 22 and 24 do reclose, they bias the controlled rectifier 54 in the same direction as the potential between junction 69 and ground both of which provide turn on bias for the controlled rectifier 54.

It will be appreciated that as the contacts 22 and 24 open and close, ignition pulses are applied to the spark plug 46 of the engine 28 in a predetermined sequence by the system of this invention and that a maximum period of on time for the primary winding 38 is achieved since the controlled rectifier 54 can be biased to its conductive state before a reclosure of contacts 22 and 24. With the use of the system of this invention, it is possible to use an ignition transformer 36 of similar design to that used with conventional breaker contacts. In addition, it is possible to use the components of the system of this invention with a conventional breaker contact distributor. With the system of this invention, however, breaker contact life is greatly increased because of the reduced current flow through the breaker contacts. In addition, better performance is achieved since higher voltages can be applied to the spark plugs 46 when the controlled rectifier 54 is used as the controlling element for primary winding current. Part of the improved performance is due to the fact that the controlled rectifier 54 can be switched back on before contacts 22 and 24 close and another part of the improved performance is due to the fact that the controlled rectifier has a high reverse breakdown voltage which permits a higher output from the secondary of the ignition coil.

The capacitor which is in parallel with the anodecathode circuit of controlled rectifier 54 protects this controlled rectifier from overvoltage of the primary 38 when the controlled rectifier turns off. The capacitor 23 suppresses the arc across the contacts 22 and 24 when they open. Resistor 70 is a current limiting resistor and as has been pointed out above, the resistors 81 and 77 form a biasing voltage dividing network.

It will be appreciated that the ignition system of this invention can be marketed as orginial equipment on new engines or could be sold as an accessory to be added to a system that has a conventional breaker contact distributor. In either case, certain components of the system can be mounted in a single package which could include resistors 67, 81 and 77, pulse transformer 64 and controlled rectifier 54 wired together as shown on the drawing. This single package could be provided with terminals corresponding to junctions 18 and 41, conductor 63 and ground, which would be connected to ignition switch 14, breaker contacts 22 and 14 and ignition coil 36 in a manner shown on the drawing. When adding the single package to an existing conventional breaker contact system, the conventional breaker contact distributor and the conventional ignition coil can be used without modification which is another advantage of this system.

Referring now to FIGURE 2, a modified controlled rectifier system is illustrated. In FIGURE 2, the same reference numerals have been used to identify the same or equivalent components in each figure. In FIGURE 2, the reference numeral 10 designates a source of direct current. One side of the source of direct current 10 is grounded and in this case, it is the negative side of the source 10 in a negative ground system. The positive side of the direct current source 10 is connected with a conductor 12 and this conductor is connected to one side of a manually operable ignition switch 14. The opposite side of the ignition switch is connected with conductor 16 which is connected to a junction or terminal 18.

The ignition system of FIGURE 2 like that of FIG URE 1 can use a conventional distributor which is used on present day passenger cars in systems where the breaker contacts directly control primary winding current. This distributor includes a pivotally mounted breaker lever 20 which carries a breaker contact 22. The breaker contact 22 cooperates with a fixed breaker contact 24 which is grounded. The breaker lever 20 is urged by a spring (not shown) to a position where the contacts 22 and 24 are in engagement. These contacts are periodically opened by a breaker cam 26 which engages a rubbing block carried by the breaker lever 20. The breaker cam 26 is driven by the engine 28. The engine also drives a rotor contact 30 which cooperates with the inserts or electrodes 32 of a distributor cap 34. In conventional practice, the distributor cap and breaker contacts are all located in one distributor all of which is well known to those skilled in the art and the rotor contact 30 and the cam 26 are driven together.

The ignition system of FIGURE 2 includes a conventional ignition coil designated in its entirety by reference numeral 36. This ignition coil has a primary winding 38 and a secondary wnding 40. The ignition coil is entirely conventional and need not be modified as to turns ratio for use in the system of FIGURE 1. In other words, the same ignition coil that is used with a conventional breaker system can be used in the system of FIGURE 1.

The secondary winding 40 of the ignition coil 36 is connected with a high voltage conductor 42 which in turn is connected to the rotor contact 30 by means of a center electrode on the distributor cap. The rotor contact 30 passes by the fixed contacts 32 and supplies ignition power to a conductor 44 connected with one side of a spark plug 46 for the engine 28. The opposite side of the spark plug is grounded and it will be appreciated that there will be six spark plugs connected respectively with the six fixed contacts 32 of the distributor cap where the system is used on a six cylinder engine. It will, of course, be appreciated that this system can be used with engines having other than six cylinders.

One end of the primary and secondary windings 38 and 40 are connected together by a conductor 48 which is ordinarily built into the ignition coil. A capacitor 50 is connected between conductor 48 and ground. The conductor 48 is connected with a conductor 52 as is clearly apparent from the drawings.

The semiconductor element for controlling primary winding current in FIGURE 2 is a controlled rectifier generally designated by reference numeral 54. This controlled rectifier has an anode 56, a gate or control electrode 58 and a cathode 60. It is seen that the anode 56 is connected with conductor 52 whereas the cathode 60 is grounded. The gate electrode 58 of controlled rectifier 54 is connected with conductor 62. The controlled rectifier 54 is the same type as that described in connection with FIGURE 1.

The ignition system of FIGURE 2 like the system of FIGURE 1 has a control transformer generally designated by reference numeral 64. This control transformer has first and second windings 66 and 68 wound on a common magnetic core. The control transformer may be also termed as a two winding inductor or a pulse transformer since its purpose is to provide voltages across the Winding 68 to bias the controlled rectifier 54 in response to periodic energization and deenergization of winding 66.

The winding 66 of the pulse transformer 64 is connected between a resistor 67 and the movable breaker contact 22. The resistor 67 is connected with junction or terminal 18 and it is seen that a resistor 70 is interposed between junction 18 and the primary winding 38 of the ignition coil 36.

A junction 72 is provided which is connected between resistor 67 and winding 66. One side of a resistor 74 is connected with junction 72, the opposite side of this resistor being connected to junction 73 which is connected to one side of transformer winding 68. The opposite side of the transformer winding 68 is connected with conductor 62 which in turn is'connected with the gate electrode 58 of controlled rectifier 54. A resistor 75 is connected between junction 73 and ground.

When the manually operable ignition switch 14 is closed, the ignition system of this invention is energized.

When the engine is being cranked by a starting motor or when it is running, the breaker contacts 22 and 24 are opened and closed in synchronism with operation of the engine.

When the breaker contacts 22 and 24 are open, current can nevertheless fiow from junction 18, through resistor 67, through junction 72, through resistor 74, through junction 73 and then through resistor to ground. As

a result of the voltaged drop across resistor 75, the junction 73 is positive with respect to ground. This causes a current flow from junction 73, through winding 68 and through the gate-cathode circuit of controlled rectifier 54. This turns on the controlled rectifier 54 in its anodecathode circuit so that current can also flow from junction 18, through resistor 70, through primary winding 38 and then through the anode-cathode circuit of controlled rectifier 54 to ground.

When breaker contacts 22 and 24 close, current can flow from junction 18, through resistor 67, junction 72, through winding 66 of inductor 64 and through breaker contacts 22 and 24 to ground. As a result of this current flow, a voltage is induced in the winding 68 which is positive on conductor 62 and negative at junction 73. This voltage will tend to increase the turn on bias for the controlled rectifier 54 and this voltage is important when the engine is being cranked since the voltage of source 10 at that time drops which tends to proportionately lower the voltage of junction 72.

With the controlled rectifier turned on in its anodecathode circuit, current flows through the primary winding 38 and magnetic flux is built up in the core of the ignition coil 36. When the breaker contacts 22 and 24 now open, a voltage is induced in winding 68 which is negative on conductor 62 and positive at junction 73. This voltage is of such a magnitude as to drive the cathode 60 of controlled rectifier 54 positive with respect to its gate 58 to therefore switch the controlled rectifier off in its anode-cathode circuit. As a result, the primary circuit for the ignition transformer 36 is temporarily interrupted and a large voltage is induced in the secondary winding 40. This voltage causes one of the spark plugs 46 to fire via a circuit that can be traced from conductor 42, through rotor contact 30, one of the fixed contacts 32 of the distributor cap, conductor 44 and then through the spark plug 46 to ground.

The voltage appearing across winding 68 which temporarily switches off the control rectifier 54 may be dissipated before the breaker contacts 22 and 24 reclose. When this occurs, the controlled rectifier 54 is switched back on by the positive voltage appearing at junction 73 which drives the gate 58 of controlled rectifier 54 positive with respect to its cathode 60. It thus is seen that the controlled recifier 54 can be switched back on before the breaker contacts 22 and 24 reclose and it therefore is possible to have a maximum on time for primary winding current with the system of FIGURE 2.

The system illustrated in FIGURE 2 is similar in operation to the system shown in FIGURE 1. It is pointed out, however, that with the system shown in FIGURE 2, the voltage at junction 72 drops when the breaker contacts 22 and 24 close. As a result, the voltage at junction 73 drops to a lower value so that the amount of current injected into the gate electrode of controlled rectifier 54 is reduced to reduce heating of this controlled rectifier. The reason for the lower Voltage at junction 72 and junction 73 when the breaker contacts 22 and 24 close is that the current flowing through winding 66 causes an additional drop across resistance '67.

Referring now more particularly to FIGURE 3, a modified controlled rectifier ignition system is illustrated. In FIGURE 3, the same reference numerals have been used as were used in FIGURE 2 to identify the same parts in each figure. In FIGURE 3, the distributor 34, the engine 28 and the breaker lever and cam are not illustrated but it will be understood by those skilled in the art 9 that the system of FIGURE 3 would be used in the same manner as that shown in FIGURE 2.

In FIGURE 3, the junction 18 is connected with the resistor 70. The opposite side of resistor 70 is connected with the primary winding 38 of the ignition transformer 36. The winding 66 of control transformer 64 is connected in series with a resistor 84 and in series with the breaker contacts 22 and 24.

The winding 68 of pulse transformer 64 has one side thereof connected with a capacitor 88 via conductor 92, the opposite side of the winding 68 being grounded through conductor 94. The opposite side of capacitor 88 is connected with the gate electrode 58 of the controlled rectifier 54 via a conductor 90.

The system of FIGURE 3 operates in a manner similar to the operation of the system shown in FIGURE 2 in that the controlled rectifier 54 can be switched back on before the breaker contacts 22 and 24 reclose. In the system of FIGURE 3, the interaction of the voltage induced in secondary 68 and the charging and discharging of capacitor 88 is such that controlled rectifier 54 is switched off when breaker contacts 22 and 24 open but the controlled rectifier can be switched back on before contacts 22 and 24 reclose.

The embodiment of FIGURE 4 is substantially identical with the embodiment of FIGURE 3 with the exception that the winding 68 is directly connected with the gate electrode of controlled rectifier 54 through a conductor 96. The opposite side of the winding 68 is connected with conductor 98 and it is seen that a capacitor 100 is connected between conductor 98 and ground. A resistor 102 is connected between conductor 98 and ground.

The capacitor 100 in FIGURE 4 performs the same function as the capacitor 88 in FIGURE 3 and the controlled rectifier 54 turns off when contacts 22 and 24 open and can turn back on before contacts 22 and 24 reclose.

Referring now more particularly to FIGURE 5, a transistor ignition system is illustrated which is capable of closing the primary circuit for the primary winding of the ignition coil before the breaker contacts reclose. In FIG- URE 5, the winding 66 of the pulse transformer 64 is connected between resistor 104 and the breaker contacts 22 and 24. One side of the resistor 104 is connected with junction 106 which in turn is connected with conductor 108. The conductor 108 is connected to one side of the ignition switch 14. The junction 106 is connected with a resistor 110, the opposite side of this resistor being connected with junction 112.

The primary winding current in the system of FIGURE is controlled by a PNP transistor which may be of the silicon type and which is generally designated by reference numeral 114. The emitter electrode of transistor 114 is connected with conductor 116 at junction 118. The base electrode of transistor 114 is connected with junction 120. A resistor 122 connects junctions 112 and 120. A resistor 124 is connected between junction 120 and one side of the winding 68 of transformer 64. The opposite side of winding 68 is grounded via conductor 126.

The collector of transistor 114 is connected with a junction 128. The junction 128 is connected to one side of a primary winding 130 of an ignition transformer 132. The secondary winding 134 of the ignition coil 132 is connected with conductor 42 which is intended to go to the center electrode of a distributor cap in the same manner as is illustrated in FIGURE 1. The primary and secondary windings 130 and 134 are connected to junction 136 which is grounded. A Zener diode 138 is connected between junctions 118 and 128 and serves to protect the transistor against high voltage transients.

When switch 14 is closed, it is seen that the transistor 114 is biased to its conductive state in its emitter-collector circuit due to current flow from junction 106, through resistor 110, through junction 112, through resistor 122, through junction 120, through resistor 124, and through the transformer winding 68 to ground. This current flow develops a voltage drop across resistor 122 which drives the emitter of transistor 114 positive with respect to its base and therefore biases transistor 114 to a conductive state in its emitter-collector circuit.

When the breaker contacts 22 and 24 close, a voltage is induced in the winding 68 which is negative at conductor 123 and positive at conductor 126. This voltage tends to increase the conductivity of the transistor 114 in its emitter-collector circuit since it in effect raises the potential of the emitter with respect to its base.

With the transistor 114 conductive in its emitter-collector circuit, current flows from junction 106, through resistor 110, through junction 118, through the emitter collector circuit of transistor 114, and then through the primary winding to ground. As a result, inductive energy is built up in the magnetic core of the ignition coil 132 due to current flow through the primary winding 130.

When the breaker contacts 22 and 24 open, a pulse of voltage is induced in the winding 68 which is positive at conductor 123 and negative at conductor 126. This voltage is of sufiicient magnitude to drive the base of transistor 114 to a potential which is equal to or positive with respect to the potential of the emitter of this transistor. When this happens, the transistor 114 switches off in its emitter-collector circuit to interrupt the circuit to the primary winding 130 and a large voltage is induced in the secondary winding 134. This voltage is then applied to a spark plug in a manner described in FIGURE 1 and pulses are periodically applied to different spark plugs as the breaker contacts 22 and 24 open and close.

It will be appreciated that the transistor 114 can be biased back to its conductive state before the breaker contacts 22 and 24 close when the turn off voltage pulse de veloped across winding 68 has dissipated. This is true because the transistor is normally biased to a conductive state by the circuit that includes resistor 122, resistor 124 and winding 68 connected between junction 112 and ground.

The embodiment of FIGURE 6 uses a transistor 140 which is of the NPN type rather than of the PNP type as shown in FIGURE 5. The same reference numerals have been used in FIGURE 6 as were used in FIGURE 5 to identify the same parts in each figure. In FIGURE 6, the base electrode of transistor 140 is connected with conductor 142. The conductor 142 is connected to one side of winding 68 of the pulse transformer 64. The opposite side of winding 68 is connected with a resistor 144 which in turn is connected with junction 146. A resistor 148 is connected between junction 150 and ground. A resistor 152 is connected between junction 146 and one side of the primary winding 130 of the ignition coil 132. The primary and secondary windings 130 and 134 of the ignition coil are connected together at junction 154 and this junction is connected with the collector of transistor 140. The emitter of transistor 140 is grounded as shown. The secondary winding 134 of the ignition coil 132 is connected with high voltage conductor 42 which goes to the distributor cap in a manner shown in FIGURE 1.

In the system of FIGURE 6, the transistor 140 is normally biased to its conductive state in its collector-emitter circuit when the ignition switch 14 is closed. When the ignition switch 14 is closed, current can flow from junction 146, through resistor 144, through transformer winding 68, and through resistor 148 to ground. The voltage drop which is developed across resist-or 148 as a result of this current flow will drive the base of transistor 140 positive with respect to its emitter with the result that the transistor 140 is switched on in its collector-emitter circuit. Current will now flow from junction 106, through junction 146, through resistor 152, through primary winding 130 and through the collector-emitter circuit of transistor 140 to ground.

If the breaker contacts are closed, current can flow from junction 185, through resistor 104, through winding 66, and through the closed breaker contacts 22 and 24 to ground. Because of this current flow, a voltage is induced in winding 68 which is positive at conductor 142 and negative at conductor 143. This biases the transistor 140 to still a more conductive condition. With current flowing through primary winding 13% inductive energy is built up in the magnetic core of the ignition coil 132.

When the breaker contacts 22 and 24 open, a voltage is induced in secondary winding 68 which is negative at conductor 142 and positive at conductor 143. This voltage has a magnitude which is sufiicient to either substantially equalize the potential of the base and emitter electrodes of transistor 140 or to drive the base electrode of transistor 140 negative with respect to its emitter. The tran sistor 140 therefor switches off in its collector-emitter circuit which interrupts current flow through the primary winding 130 which in turn causes a high voltage to be induced in the secondary winding 134. This voltage is applied to a spark plug via high voltage conductor 42 and a distributor capin the same manner as illustrated in FIGURE 1. A Zener diode may be connected across the transistor 140 for transient voltage protection if desired.

While the embodiments of the present invention as herein disclosed constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An ignition control circuit adapted to be connected with an ignition coil, a pair of distributor breaker contacts and a source of direct current comprising, inductor means having a first and second magnetically coupled windings, a controlled rectifier having anode, cathode and gate electrodes, said controlled rectifier being of a type which can be switched on and ofif in its anode-cathode circuit by varying the relative potential of its gate and cathode electrodes, a first conductive circuit adapted to be connected between one side of a source of direct current and the breaker contacts of a distributor including said first Winding of said inductor means, the anode-cathode circuit of said controlled rectifier being adapted to be connected in series with a source of direct current and in series with the primary winding of an ignition coil, and a capacitor, said capacitor being connected in series with said second winding of said inductor means and in series with the gate-cathode circuit of said controlled rectifier.

2. An ignition system for an internal combustion engine comprising, a controlled rectifier having anode, cathode and gate electrodes, said controlled rectifier being of a type which can be switched on and off in its anodecathode circuit by varying the relative potential of its gate and cathode electrodes, an ignition coil having a primary winding and a secondary winding, a source of direct current, means connecting the anode-cathode circuit of said controlled rectifier and the primary winding of said ignition coil in series with said source of direct current, inductor means including first and second windings, a

control circuit connected across said source of direct current and including switching means, said first winding of said inductor means, a capacitor, and a series loop circuit including said capacitor, said second winding of said inductor means and the gate-cathode circuit of said controlled rectifier, said capacitor both charging and discharging between consecutive switch openings of said switching means to vary the potential of said controlled rectifier gate electrode so that said controlled rectifier is switched both off and on.

3. The combination according to claim 2 wherein the switching means of said control circuit includes a pair of breaker contacts driven by said engine.

4. The combination according to claim 2 wherein said switching means of said control circuit opens and closes in synchronisrn with operation of said engine.

5. The ignition system according to claim 2 wherein the capacitor is connected between one end of the second winding of the inductor means and the gate electrode of the controlled rectifier.

6. The ignition system according to claim 2 wherein the capacitor is connected between one side of the second winding of the inductor means and one side of said source of direct current.

7. An ignition control circuit adapted to be connected with an ignition coil, 21 pair of distributor breaker contacts and a source of direct current comprising, inductor means having primary and secondary magnetic coupled windings, a controlled rectifier having anode, cathode and gate electrodes, said controlled rectifier being of the type which can be switched respectively on and off between the anode and cathode electrodes by opposite polarity voltage impulses applied between the gate and cathode electrodes, a first conductive circuit connected between one side of the source of direct current and the breaker contacts of a distributor including said primary winding of the inductor means, the anode-cathode circuit of said controlled rectifier being connected in series with said source of direct current and with the primary winding of an ignition coil, and a series connected gating control circuit including said secondary winding of said inductor means, a capacitor, and the gate-cathode electrodes, said capacitor discharging through the series circuit in one direction when said breaker contacts are opened to switch said control rectifier off and said capacitor recharging in an opposite direction while said breaker contacts remain open to switch said control rectifier on prior to the subsequent closing of said breaker contacts.

References Cited UNITED STATES PATENTS 2,878,298 3/1959 Giacoletto. 3,049,642 8/1962 Quinn 3l5206 3,213,320 10/1965 Worrell 3 l5209 LAURENCE M. GOODRIDGE, Primary Examiner. 

